A web of merely glass fibers such as the Owens-Corning DE 636 (described in Example 1 below) bound with polyvinyl alcohol (98% hydrolyzed) was made but its use had been rather restricted. For example, it has been used as a battery plate separator and as the base for roof covering to be coated over with tar. However, no such web of glass fiber and polyvinyl alcohol (i.e. called PVA) has been known for use in any such treatment of fluids as described above.
For many years various industries have been concerned with troublesome solid particles of fine droplets of liquids or harmful gases released into working areas and often passing through vents or smoke stacks into the outside atmosphere, thus provoking bothersome evnironmental problems. In some cases, it has been merely dust particles from working with inorganic materials such as recovering minerals from ores or grinding and polishing operations.
In other cases also involved are liquid droplets entrained from chemical operations such as electroplating, spray coating of one kind or another or production of certain synthetic resins. In still other situations it may be harmful gases, for example, sulfur dioxide carried into the atmosphere as from burning of high sulfur content fuel oils or bituminous coals. Production of a polyphenylene oxide-polystyrene alloy polymer involves release in part of resin fines or pellets, dust particles and of oily plasticizer droplets entrained apparently as an aerosol into the air.
Some attempts to overcome some of these problems have been made by using (i) a filter medium such as a mat of glass fibers held together by a phenol formaldehyde resin binder, or (ii) glass wool air filters in window openings or other outlets. However, generally these filter media are bulky and yet not dense enough to restrain the finer particles or gases, thus still allowing undesirable fluid passage through them and thereby still to pass out to the atmosphere. Then also some of these mats, among other shortcomings, have an undesirably limited tensile strength resulting in too frequent breaks requiring interrupting their use in undue time-consuming repair.
Other attempts include use of electric charging precipitators, such as the long known Cottrell electric precipitators, but these are costly to install, operate and maintain, and do not restrain merely gases, for example, sulfur dioxide.
These disadvantages are overcome by the gas-vapor filter of treating mats of the invention. Then too, these mats of the invention show enhanced porosity and tensile strength over the above described glass fibers and PVA webs used as battery separators and in roof covering sheets.